初二数学题（整式的乘法）急用!①若（2x+y-1）的二次方+|x-2y-3|=0,求代数式(2x+y)(2x-y)-(x
3个回答
1.（2x+y-1)^2+|x-2y-3|=0
2x+y-1=0,x-2y-3=0
x=1,y=-1
(2x+y)(2x-y)-(x+2y)(x-2y-1)
=4x^2-y^2-(x+2y)(x-2y)+(x+2y)
=4x^2-y^2-x^2+4y^2+x+2y
=3x^2-3y^2+x+2y
=3-3+1+2*(-1)
=-1
2.（2x+3）(3x+2)-6x(x+3)+5x+6
=6x^2+4x+9x+6-6x^2-18x+5x+6
=12
代数式（2x+3）(3x+2)-6x(x+3)+5x+6的值与x的取值无关.
3.(x^2+px+8)*(x^2-3x-q)
=x^4-3x^3-qx^2+px^3-3px^2-pqx+8x^2-24x-8q
=x^4+(-3+p)x^3+(-q-3p+8)x^2+(-pq-24)x-8q
积中不含 x的三次方 与x项
-3+p=0,-pq-24=0
p=3,q=-8
4.：（x-y）[（x+y）(x+y)-xy]+(x+y)[(x-y)(x-y)+xy]
=(x-y)[x^2+2xy+y^2-xy]+(x+y)[x^2-2xy+y^2+xy]
=(x-y)(x^2+xy+y^2)+(x+y)(x^2-xy+y^2)
=x^3-y^3+x^3+y^3
=2x^3
：（x-y）[（x+y）(x+y)-xy]+(x+y)[(x-y)(x-y)+xy]的值是2x^3, 它的值与 y无关
5.a*b=ab+a-b
a*b+（b-a）*b=ab+a-b+(b-a)b+(b-a)-b
=ab+a-b+b^2-ab+b-a-b
=b^2-
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